Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
  • D01F2/06—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from viscose
  • D01F2/08—Composition of the spinning solution or the bath

Definitions

• the present invention relates to the manufacture of viscose rayon and more particularly to a process in which viscose is spun into an acid spinbath and subsequently highly stretched in a hot dilute acid bath to produce yarn of controlled low elongation.
• the strength of viscose yarn can be increased by stretching the same, preferably Within a short time after it leaves the spanbath. And it is thought that the strength increases in direct proportion to the increase in stretch.
• the system generally used is known as the two-bath spinning process and includes a normal spinbath containing sulfuric acid and salts such as sodium sulfate and zinc sulfate, and a second weakly acidic bath which is maintained at a high temperature, for example, in the neighborhood of 90 C. and above.
• the yarn have not only a high strength but also a low elongation.
• it is possible to reduce the elongation by increasing the stretch imparted to the yarn it has been found that after a point the elongation may not be reduced by additional stretching.
• the elongation is undesirably high even by employing a high stretch, it has been the practice heretofore to give the yarn a final stretch in a wet condition. Thereafter, this yarn is dried under tension.
• the yarn upon being wet again, the yarn has a great tendency to shrink. This shrinkage is just as undesirable astoo high an elongation in many industrial applications. Consequently, the need exists for a spinning process by which a high strength, low elongation yarn maybe produced.
• An object of the present invention is, therefore, to provide a process for increasing the stretchability and strength and for reducing the elongation of viscose yarns.
• Another object of the present invention is to provide a new acid spinbath composition useful in producing .viscose'yarn having the aforesaid desirable properties.
• the threads produced in accordance with the invention have lower elongation and can withstand a higher spinning stretch than yarn obtained from normal spinning. Furthermore, this high stretch may be attained at a lower stretching tension.
• the stretchability of the freshly spun threads at the low spinbath temperature is so great, depending on the combination of viscose and spinbath variables, that it is possible to stretch the threads up to 100% and more in the one-bath process, which values were thought to be restricted to the two-bath process.
• the temperature of the second dilute bath may be kept lower than otherwise considered necessary, if the present invention is followed. For example, temperatures of 50 C. to C. are sufiicient in order to achieve the amount of stretch which formerly could be obtained at temperatures much higher than 70 C. in the second bath.
• An additional important advantage of the process according to the present invention lies in the fact that it is possible to vary within limits the ratio between the breaking load and breaking elongation. It is known that with every spinning process the numerical value of this ratio can be somewhat modified by various changes in the spinning conditions. However, for given spinning conditions it is possible by the present invention to control the resulting elongation during the manufacturing of the articles to a greater extent than in normal spinning. Thus, there is more flexibility in adapting the yarn to meet the physical property requirements of the customer.
• the present process has proved to be of particular value in those cases where yarns with difierent elongation values are to be spun from a common spinning bath installation to different spinning machines.
• the present invention it is only necessary to adjust the bath temperature at the machines to difierent levels.
• the present invention also contemplates spinning in the presence of an additive which modifies the regenerating-coagulating process of the viscose.
• additives are referred to generally in the art as viscose modifiers.
• the yarn produced under the influence of a viscose modifier has many distinctive characteristics that distinguishes it from normally spun yarn. For example, cross sections of the filaments produced in a system employing a modifier when stained and viewed under a microscope in a well known manner reveal a skin-type of yarn having a periphery of notably reduced crenulations.
• the modifiers may be used in various amounts, depending upon the spinning conditions and the particular modifier employed. However, in general, the modifiers may be used in various amounts, depending upon the spinning conditions and the particular modifier employed. However, in general, the modifiers may be used in various amounts, depending upon the spinning conditions and the particular modifier employed. However, in general, the modifiers may be used in various amounts, depending upon the spinning conditions and the particular modifier employed. However, in general, the modifiers may be used in various amounts, depending upon the spinning conditions and the particular modifier employed. However, in general, the
• the '3 concentration for addition to the viscose is 0.02%.
• the modifier is added in the amount of about 0.02 to 0.6%.
• the preferred concentration is in the range of 0.1 to 5.0 g. per kg. of spinbath.
• both the advantages of modified spinning and the advantages of using the low acid spinbath maintained at a low temperature may be obtained cumulatively. This is surprising in view of the fact that when certain modifiers are used threads of high elongation may result.
• Yarns of extremely high strength can be produced by using viscose additives at spinbath temperatures lower than 50 C.; for example, yarns having strengths of 500 g./ 100 denier and higher (air-dry) may be obtained.
• the bath Besides the critical acid concentration of the spinbath, other components of the spinbath are important to the present invention. Ordinarily, it is required that the bath contain a zinc salt, preferably Zinc sulfate in the amount of at least 2% by weight. Amounts as high as 15% zinc sulfate are satisfactory in some cases. The relatively high cost of the zinc salt and the concentration of the other components of the bath are factors to be considered in selecting the amount. If necessary, the zinc sulfate may be replaced partially with iron sulfate.
• a zinc salt preferably Zinc sulfate in the amount of at least 2% by weight. Amounts as high as 15% zinc sulfate are satisfactory in some cases. The relatively high cost of the zinc salt and the concentration of the other components of the bath are factors to be considered in selecting the amount. If necessary, the zinc sulfate may be replaced partially with iron sulfate.
• the bath may contain'other substances ordinarily employed in viscose rayon manufacture. For example, it may contain a very small amount of surface active agents and sodium sulfate. In the present invention it is preferred that the spinbath contain 5 to 20% sodium sulfate. For best results, it has been found that the ratio of the percentage of sodium sulfate to the percentage of zinc sulfate should be between 1.0 and 2.4.
• the stretchability of the freshly spun viscose yarn is increased; and in addition thereto, by adapting the bath temperature to the stretch, it is consequently possible to control the elongation of the yarn as required and still to provide a considerable latitude for bringing the other yarn properties to a most favorable value.
• EXAMPLE I Alkali cellulose prepared and aged in the usual manner was xanthated with 38% C8 based on the cellulose. The xanthate crumlbs were dissolved in a solution of sodium hydroxide to produce a viscose having a cellulose content of 6.5% by weight and an alkali content of 5.7% by weight. The viscose was filtered, deaerated and aged for 48 hours to a maturity of 47 gamma number.
• This viscose was extruded through a spinneret immersed in a spinbath having the composition by. weight of 4.7% H 80 10% Na SO and 7% ZnSO
• the spinneret employed had 1000 orifices, each having a diameter of 60 microns.
• the yarn produced thereby had a denier of 1650.
• the temperature of the spinbath was maintained at 38 C.
• the yarn was given a bath travel of 60 cm. after which it was withdrawn by means of a first godet.
• the yarn was then carried through and stretched in a second bath by means of a second godet and guided there- 'through by means of a pair of freely rotatable rollers immersed in the second bath.
• the second bath contained 2% H 80 and had a temperature of 93 C.
• the yarn withdrawal speed produced by the second godet was 35 meters per minute.
• the stretching tension on the yarn as measured between the point at which the yarn is removed from the second bath and the point at which the yarn is taken up by the second godet was maintained at 1500 g.
• the yarn was aftertreated in the usual way.
• yarn was produced in identical manner as described above except the temperature of the spinbath was maintained at 60 C. In each case the yarns were dried without tension.
• the properties of the yarns together with the stretch-imparted therein by the 1500 g. stretching tension are listed in Table l.
• Cord made from the yarn using the lower temperature spinbath shows a reduced elongation at break.
• the yarn spun at 38 C. only had to be given an after stretch of 5%.
• the other yarn to obtain the same elongation had to be given an after stretch of 10%.
• the shrinkage force i.e., the force necessary to neutralize the tendency of the yarn to shrink when rewet, was about one-half as much as compared with the second mentioned yarn.
• Example I A comparison with the results of the carried out-at 60- C. in Example I shows that employing the lower bath temperature not only reduces elongation also increases the strength of the yarn. With even lower bath temperatures, it is possible to obtain even lower elongations while maintaining the high strength, as shown by the following example.
• EXAMPLE in Two dififerent viscoses were prepared and each spun in the manner described in Example Iinto different spinbaths.
• the viscose and spinbath compositions were so chosen that one process would produce yarn having a relatively low elongation and the second process would produce yarn having a relatively high elongation.
• Each combination was spun at two different temperatures in order to influence the elongation.
• the type of yarn with the lower elongation (experiments 1 and 2 in Table III) was spun at 40? C. and 55 Q, while the other type (experiments 3 and 4 in table III) was spun at 25 C. and 44 C. and produced substantially the same corresponding elongations.
• Table III gives the viscose compositions, spinbath compositions, spinbath temperature and the amount of stretch in the hot acidic second bath, together with the properties of the yarn produced therefrom.
• the yarn was in an oven-dried condition and had not been given a final stretch.
• EXAMPLE IV A viscose with a composition of 6.4% cellulose and 5.8% alkali was extruded in the manner described in Example I into a primary spinbath having a temperature of 39 C. and containing 9.5% Na SO and 8.5% ZnSO The viscose had been ripened for 72 hours to a maturity of 43 gamma number.
• the spinbath acid content was varied as indicated in Table IV.
• the freshly spun threads were stretched 114% in the spinbath.
• the threads were given the three different acid concentrations are given in Table IV.
• the yarns physical properties are favorably influenced by spinning at low temperatures. For example, with 3.8% H 80 the swelling is lower and and the strength is higher than when a spinbath temperature of 60 C. is used as in Example I. Also, the cord properties show corresponding improvements.
• the viscose was spun at a gamma number of 48 into a spinbath having the composition of 5% H 10% Na SO and 8% ZnSO Spinning was conducted with the temperature of the spinbath being maintained at four differentlevels.
• Other conditions such as composition and temperature of the secondary bath, aftertreating of the. yarn, and the like, were identical to those of Example I.
• the yarn properties together with the stretch given the yarn in the secondary bath may be seen by reference to Table V.
• EXAMPLE VI Viscose containing 6.5% cellulose and 5.8% alkali was prepared as in Example I and spun at a gamma number of 48 into a spinbath having the composition of 5% H 50 10% Na SO 8% ZnSO and 0.05% of the ethoxylated aliphatic amine described in Example V. Spinning was conducted while maintaining the temperature of the spinbath at diiferent temperatures, above and within the preferred range of the present invention. The low spinbath temperatures gave much higher yarn strength and reduced elongation than the normal high temperature spinning.
• Viscose containing 6.5% cellulose and 5.8% alkali was prepared as in Example I. 0.2% of the additive employed in Example V was incorporated into the viscose. Spinning was carried out with the spinbath being maintained at temperatures of 30 and 44. In both cases the yarns were stretched in the secondary bath. The influence of the spinbath temperature on the yarn may be seen by reference to Table VI wherein the physical properties of the yarns are listed.
• the stretching tension at the lower spinbath temperature was about 500 g. less. Of course, even better elongation could be obtained by completely utilizing the higher stretchability of the yarn produced at the lower temperature.
• EXAMPLE VIII Viscose containing 7.3% cellulose, 5.0% alkali and 0.2% of the amine additive described in Example V was spun into a spinbath having the composition of H 80 Na SO and 8% ZnSO A corresponding relationship between the spinbath temperature on one hand and the stretchability, draw tension and yarn elongation on the other hand was obtained. For example, by using this viscose containing the additive at the low spinbath temperature of the present invention, it was possible to obtain yarn having an air-dry strength of 5'00 g./100 den. and in some instances even higher.
• EXAMPLE 1X Viscose containing 7.3% cellulose, 5.0% alkali and 0.2% of the amine viscose modifier described in Example V was spun into a spinbath having the composition of n 5% H 50 14% Na 'SO and 6% ZnSO A comparison of the yarn properties produced with the spinbath maintained at 57 C. and 46 C. showed that the lower temperature spinning caused a lowering of the cord elongation firom 21% to 18% the air-dry condition and higher yarn stretchability, a yarn of greater strength was produced.
• a process for the production of high strength viscose yarn having increased stretchability and low elongation comprising spinning a viscose into a spinbath maintained at a temperature of 38 C. to 39 C. and containing 4 to 6% sulfuric acid, 2 to 15% zinc sulfate and 5 to 20% sodium sulfate, the ratio of the percentage of sodium sulfate to the percentage of zinc sulfate being between 1.0 and 2.4, withdrawing the freshly spun yarn from said spinbath and stretching the yarn in a second hot Weakly acidic bath.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Artificial Filaments (AREA)

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  • 1956-08-29 DE DEV11130A patent/DE1100871B/de active Pending
  • 1956-08-29 DE DEV10959A patent/DE1041205B/de active Pending
• 1957
  • 1957-06-28 GB GB20551/57A patent/GB813233A/en not_active Expired
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